SEMANTIC PROCESSING AND ORTHOGRAPHIC SPECIFICITY IN HEMISPATIAL NEGLECT

Two sets of experiments, each consisting of a semantic priming task an d a discrimination task, investigated the proceedings of lexical infor mation in the neglected visual field. In the semantic priming task, su bjects made lexical decisions to target words preceded by lateralized word primes; in the discrimination task, they indicated which of two w ords corresponded to a target word presented to the left visual field (LVF) or right visual field (RVF). The first set of experiments indica ted that although patients were unable to discriminate words presented in the LVF,they showed significant priming when LVF primes were follo wed by semantically related targets compared to unrelated targets. The second set of experiments further examined the nature of this priming effect by comparing priming in a condition in which primes were seman tically related to the target word (e.g., TEA-CUP) and a condition in which primes were unrelated to the target word, but orthographically s imilar to a related prime (e.g., PEA-CUP). This experiment replicated the previously established semantic priming effects and demonstrated s ignificant negative priming for targets preceded by LVF primes that we re orthographically similar to a semantically related word. Again, pat ients performed at chance in the forced-choice discrimination task whe n targets were presented in the LVE These findings indicate that seman tic processing of neglected lexical information is based on hilly spec ified perceptual and orthographic information. A lateral inhibitory me chanism is proposed that maximizes the probability, albeit unsuccessfu lly, that neglected orthographic information will reach awareness.